More than a dozen bookstores, artists and Internet service providers have joined the ACLU in suing the state Thursday to prevent enforcement of a new Utah anti-pornography law.

The lawsuit was filed in federal court by 15 plaintiffs and challenges the constitutionality of HB260, which was passed by the 2005 Legislature.

"The law is meant to protect children from material considered inappropriate for minors but is constitutionally protected for adults," said Michael Bamberger, a New York attorney representing the plaintiffs. "But there's no practical way of determining what a minor is looking at."

At a news conference at the King's English Bookstore, the lead plaintiff in the suit, co-owner Betsy Burton said the store's Web site includes descriptions and jacket images from books such as D.H. Lawrence's "Lady Chatterly's Lover" and Henry Miller's "Tropic of Capricorn." While Burton said the information on her site is constitutionally protected, she worries it might land her on the Adult Content Registry and face possible criminal charges.

The registry, under the new law, will be a list of Internet sites that the Utah Attorney General's Office determines have adult content that could be blocked by certain Internet service providers for certain users. The law would also allow third-degree felony charges to be filed against people for distributing material potentially harmful to minors if the person fails to determine the age of the minor, ACLU attorney Margaret Plane said.

Lawyers said Utah's statute was worse than similar laws found unconstitutional in other states because it provides no way for Web hosts to appeal judgments made by Utah's Attorney General's Office about what constitutes a pornographic site.

"We're a community bookstore. We serve students, teachers, adults and children, and we have a Web site to accommodate that," Burton said. "Unless I limit the Web site to children's books or attempt to exclude children, I risk the danger of a criminal charge."

The lawsuit, which seeks an injunction against enforcing the law, claims the new law violates the Constitution's First, Fifth and 14th amendments as well as the federal commerce clause.

Utah Attorney General Mark Shurtleff had no comment on the lawsuit, but his spokesman said the state would meet with the plaintiffs' attorneys.

Bamberger said the plaintiffs are looking to resolve the matter quickly "so the taxpayers of Utah are not charged too much for defending a law that is unconstitutional and will be defeated in the end."

In addition to contentions against the registry, plaintiffs also complained about the provision that requires Internet service providers to block sites on the registry under certain circumstances.